The present invention relates to a negative working light-sensitive composition and in particular to a light-sensitive composition suitably used for preparing a presensitized plate for use in making lithographic printing plates, which is excellent in developability with an aqueous alkali developer.
Most of the materials which are used as light-sensitive substances for negative working presensitized plate for use in making lithographic printing plates (hereinafter referred to as "PS plate(s)") are diazonium compounds, and most commonly used are diazo resins such as a condensate of p-diazodiphenylamine and formaldehyde.
Compositions for the light-sensitive layer of PS plates in which a diazo resin is used can be divided into two groups, one of which simply comprises diazo resins, in other words those free of binders as disclosed in U.S. Pat. No. 2,714,066; and the other of which comprises a mixture of a diazo resin and a binder as disclosed in U.S. Pat. No. 4,275,138[Japanese Patent Un-examined Publication (hereunder referred to as "J.P. KOKAI") No. 50-30604]. However, most of the recent light-sensitive compositions for PS plates in which diazonium compounds are used comprises a diazonium compound and a polymer serving as a binder to achieve high printing durability.
As such a light-sensitive layer, there have been known so-called alkali-developable ones whose unexposed areas are removed or developed with an aqueous alkaline developer; and so-called solvent developable ones whose unexposed areas are removed with an organic solvent type developer as disclosed in U.S. Pat. No. 4,275,138[Japanese Patent Publication for Opposition Purpose (hereinafter referred to as "J.P. KOKOKU") No. 52-7364]. However, the alkali developable ones have become of major interest lately from the viewpoint of safety in work operations and health of operators. Examples of binders useful in such an alkaline developable light-sensitive layer include polymers obtained by copolymerizing 2-hydroxyethyl(meth)acrylate and a carboxyl group containing monomer such as methacrylic acid as disclosed in the aforesaid U.S. Pat. No. 4,275,138(J.P. KOKOKU No. 52-7364); polymers obtained by copolymerizing a monomer having aromatic hydroxyl group(s) and a carboxyl group containing monomer such as methacrylic acid as disclosed in J.P. KOKOKU No. 57-43890; polymers obtained by reacting residual hydroxyl groups of polyvinyl acetal resin with an acid anhydride and then reacting a part of the resultant carboxylic acid with a halogen compound having hydroxyl or cyano group(s) as described in U.S. Pat. No. 4,741,985(J.P. KOKAI No. 61-128123); polymers prepared by reacting sulfonyl isocyanate with a polymer having free OH group(s) as described in U.S. Pat. No. 3,732,105(J.P. KOKAI No. 47-9902); and polyurethane resins carrying substituents having acidic hydrogen atom(s) as described in DE No. 3716607A[Japanese Patent Application Serial (hereinafter referred to as "J.P.A.") No. 62-121666]. However, further improvement in the developability of these light-sensitive layers conventionally proposed have been required.